Hmm. For some reason, highscores are not saving/loading for me. If I keep hiscore.dat in the base Mame folder (with the executable), I see that .hi files are created in the hi folder, but are not apparently recognized by Mame; upon reloading a game, the original high scores are displayed. If I move the hiscore.dat file to the hi subfolder, no .hi files are created, and thus, no high scores are saved either. Not sure what's wrong. I'm using the latest 0.169 patch, and am running Manjaro Linux (a derivative of Arch).
EDIT: Well, I've found a workaround solution; for some reason, copying hiscore.dat to both the base Mame folder AND the hi folder solved the problem; high scores now both save AND load as expected. ...Odd, but a solution for me nonetheless...